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Sodium concentration in serum/plasma

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of sodium, a key electrolyte, in your blood. Sodium helps balance fluids and maintain proper heart and nerve function.

Quick summary

["Sodium levels help doctors check for dehydration, kidney issues, or other health concerns."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
93997-5
Short code
Sodium 1h p Vaso SerPl-sCnc
Synonyms
Sodium 1h p Vaso SerPl-sCnc
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
136
Ref high
145
Critical range
120 N/A – 160 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84295
SNOMED
110741000
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test if you have symptoms like excessive thirst, confusion, muscle cramps, or swelling. It’s also used to monitor conditions like heart disease, kidney problems, or high blood pressure.

What to Expect Before the Test

No special preparation is needed, but avoid eating or drinking anything (except water) for 8–12 hours before the draw if instructed. Bring your doctor’s notes or recent test results if you have them.

How the Test Works

A small needle will draw blood from a vein in your arm. The blood is sent to a lab where it’s analyzed for sodium concentration using an automated method.

What the Results Mean

Results are compared to a standard range, but exact values can vary by lab. Low sodium (hyponatremia) or high sodium (hypernatremia) may signal health risks.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium Level

Frequently asked questions

What causes low sodium levels?
Low sodium can result from excessive sweating, vomiting, diarrhea, kidney problems, or certain medications (e.g., diuretics). It may also occur if you drink too much water without balancing electrolytes.
What causes high sodium levels?
High sodium is often linked to dehydration, kidney failure, excessive salt intake, or conditions like diabetes insipidus. Rarely, it can be caused by hormonal imbalances.
Can I adjust my diet to help sodium levels?
Yes, if your doctor approves: Reduce salty foods, drink more water (unless advised otherwise), and avoid excessive sweating. Always follow their guidance based on your specific results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy